1. Field of the Invention
The present invention relates generally to video distribution systems and, more particularly, to a method and apparatus for classifying video flows to minimize switching time at a user terminal.
2. Description of the Background Art
Television-based entertainment systems are expanding the programming and services that they offer. In addition to television programming content such as that found on broadcast and traditional cable networks, television service providers are adding on-demand video, as well as other interactive services, features, and applications. The existence of these specific services, features, and applications, as well as the continuing increase in the breadth of available general programming content, drives the adoption of digital network technology for television-based entertainment systems by broadcast, satellite, and traditional cable networks. In addition, such digital network technology is being offered by other forms, such as Internet Protocol Television (IPTV).
IPTV describes a system where a digital television service is delivered to subscribing customers using IP over a broadband connection. Exemplary broadband connections include digital subscriber line (DSL) connections and data-over-cable service interface specification (DOCSIS) cable connections. IPTV service is often provided in conjunction with video on demand (VOD) and may further include Internet services and voice over internet protocol (VOIP) services. In an IPTV system, video flows traverse one or more packet networks before being distributed to clients. Due to variable transmission delays through the packet network(s), individual video flows suffer from variable delays at the client receiving equipment, referred to as “network jitter” or “jitter.”
Client receiving equipment (e.g., a set-top box) typically includes jitter compensation logic that buffers an incoming video flow before decoding. At a minimum, the fill level of the buffer must be more than the jitter of the video flow. Presently, since the receiving equipment can select from several video flows (e.g., channels), the receiving equipment sets the buffer fill level high enough to accommodate the largest expected jitter for all possible video flows. Such a high fill level, however, causes the switching time between video flows (channel changing time) to be higher than necessary for those flows that have low jitter. Accordingly, there exists a need in the art for a method and apparatus for minimizing switching time at a user terminal for video flows.